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Breaking glass - chemical change

popsicle - physical

milk - chemical

bread - physical

roasting - chemical

egg - chemical

fireworks - chemical

mixing something with water - chemical

popcorn - chemical

colouring hair - physical

melting chocolate - physical

crumpled paper - physical

rusted nails - chemical

crushed can - physical

cooked egg - chemical

bending metal - physical

melting ice - physical

bleaching clothes - chemical

If u want to differentiate between chemcial and physical change u need to remember this-

physical change - no new substance is formed (Even for melting of ice it's still water) and it can be reversible, except for some cases like tearing of paper

chemical change - a new substance is formed

cc jyfu65   6r 67r   r576dyfu r6tyuio fghjkl;

- calcium has greater affinity to bond with electron receptors than hydrogen does and hence, it has the ability to replace hydrogen in most of its compounds.

- lithium has 2 valence electrons in the product because it can make only 1 bond with hydrogen. beryllium has 4 valence electrons in the product because it can only make 2 bonds. it has fewer electrons than neon and can react with electron donors. each hydrogen has 2 valence electrons, the same as helium.

- the covalent bond formed between carbon and hydrogen is polar because carbon is more electronegative than hydrogen and it attracts the bonded electron pair closer to itself, thus giving hydrogen a partial positive charge.

- a hydrogen bond is a relatively weak bond that hydrogen atoms make with the electronegative atoms nitrogen, oxygen or fluorine.

so the best choice is a.) 2 calcium (ca) atoms