a) I'll take these shoes with me in case it rains..)
b) I'll take these shoes with me if it rains. .

معرفة الفرق بين الجملتين تقتضي معرفة الفرق بين in case و if ويتلخص ذلك في الاتي :
1- in case تعبر عن ان الحدث الذي بعدها سيحدث من باب الاحتياط a precautionary action/an emergency preparation/a precaution والحدث الذي يُذكر قبل in case يحدث اولا قبل الحدث الذي يُذكر بعدها .لاحظ الفائدة/الخلاصة التالية :
In case = because something might happen later or before something happens/might happen later
2- if تعبر عن شرط يليه حدوث نتيجة وحدوث النتيجة يقتضي حدوث الشرط اولا .لاحظ الفائدة/الخلاصة التالية :
if something happens = if something has already happened
اي ان : مع if نفعل شيء عند انتهاء حدوث شيء اخر او عند/بعد حدوثه فعلا ومع in case نفعل شيء اولا لمجرد الاحتياط من حدوث شيء اخر .
مثال للتوضيح :
Let's go to the airport in case dad comes
هذه الجملة تحمل نفس معني الجملة التالية :
Let's go to the airport now because dad might come later
ولكن نفس المثال مع if :
Let's go to the airport if dad comes
هذه الجملة تحمل نفس معني الجملة التالية :
Let's go to the airport if dad has already come
او
Let's go to the airport after/when dad has already come/comes
خلاصة اخيرة :
مع in case نفعل شيء قبل اخر احتياطا لو وقع ومن ذلك نفهم انه قد يقع او لا يقع لكن الاحتياط سوف يُجرَي علي ايه حال.
مع if نفعل شيء بعد التأكد من حدوث شيء آخر او عند/بعد حدوث/تمام شيء اخر اي ان if تفيد بيان شرط وقوع حدث عند/بعد وقوع حدث آخر فعلا .

هذا الشرح كامل و موثوق وارجوا ان يستفيد به الاعضاء والزوار فهو غير منسوخٌ ولا مسروقٌ وخلاصة قراءة كثيرة عن الفرق بين if/in case فــ اللهم اجعل عملنا كله خالصا لوجهك الكريم .
ملحوظة : تم استخدام مزيج ممتع من الالوان لطرد الملل عند القراءة ولجعل الموضوع اكثر امتاعا وسهولة ولو ركزت في الالوان ستجد نمطاً مُتَّبعاً لو فهمته سيساعدك علي الاستيعاب اكثر.
عزيزي(تي) القاريء(ة) إن اعجبك الشرح فلا تبخل علينا بدعوة عن ظهر الغيب ..
تحياتي للرائع مستر ابو بيشو علي اثارة مثل هذه الاسئلة المفيدة.
:rolleyes: My Regards
Mr.Khaled Mohammed Zalat

شكرا جزيلا لك عزيزى مستر خالد عمل رائع من معلم اكثر من رائع اليك منى كل احترام وتقدير

a) I'll take these shoes with me in case it rains. (I'll take the shoes whether it rains or not, because there is a risk of rain.)
b) I'll take these shoes with me if it rains. (I will not take the shoes if it does not rain.)

What’s the difference between “if” and “in case”
It is important not to confuse “if” and “in case”. They can be used in similar sentences, but they have different meanings. Consider the following examples:
 I will take a coat if it rains.
 I will take a coat in case it rains.
Here, “if” is used to present a conditional situation (dependent it raining), while “in case” is a precaution (done to prepare for the rain).
“In case” is usually used to show that an action is being taken, or preparations have been made, as a precaution – so the action or event is completed based on a possibility.
 I have bought extra porridge in case we need more.
 He was expecting a delivery, so he stayed at home in case it arrived.
“If”, as a conditional, shows an action or event that is dependent on something else happening. The action will not happen unless the if clause happens.
 I will go to the play if I have some spare time.
 She will receive a reward if she passes her exam.
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Using “if” and “in case”
For sentences where it seems that both can apply, “if” and “in case” can therefore refer to completing actions at different times – “in case” actions are done in advance, while “if” actions only occur on a condition. Consider these examples:
 Call me if you need any help.
 Call me in case you need any help.
The first sentence tells you to call only when you need help, the second sentence tells you to call before you need help (and in this case may be to check whether or not you need help).
 We’ll proofread the report in case there are mistakes.
 We’ll proofread the report if there are mistakes.
The first sentence here says it will be done anyway, to find mistakes, but the “if” sentence tells us there will be no proofreading unless a mistake is found first.
Sometimes the difference can be subtle, such as when a precaution is already in place but will only be relevant if a condition occurs.
 She can give you advice, in case you need help.
 She can give you advice, if you need help.
The first sentence emphasizes that she is prepared to give advice, as a precaution, while the second sentence shows she will give advice if it is needed. The two sentences are very similar, but have grammatically different meanings.

In case
We use in case to talk about taking precautions, doing something because something else might happen:
• During the drought, keep the bath filled with water - just in case it is needed.
• I've bought some candles in case there are more electricity cuts.
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• In case I forget, remind me to check the tyre pressure before we load up the car.
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In case or if?
When we use in case we are mostly describing future possible situations. When we use if we are talking about conditions that apply. Compare the following and note the differences in meaning.
• I'll fill up the car with petrol in case you need to go to Brighton. ( = I'll fill up now, because you might need it later.)
• I'll fill up the car with petrol if you need to go to Brighton. ( = Let me know if you need to go to Brighton and then I'll fill up with petrol.)
• Take the mobile phone with you in case the car breaks down.
If the car breaks down, give me a ring.
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in case of
Note that in case of is a prepositional phrase used with a noun which is similar in meaning to an if-clause. Compare the following:
• In case of fire, exit from the building by the stairs. Do not attempt to use the lift.
• If there is a fire, leave the building via the stairs. Don't try to use the lift.
• In cases of difficulty, phone this help line.
If you experience any problems, phone this help line.